System and method for cooling electronic systems

ABSTRACT

A cooling system for cooling a plurality of electronic components comprises a centralized source comprising at least one micro cooler configured to deliver a flow of a cooling medium and a plurality of baffles configured to redistribute the cooling medium over the electronic components. The electronic components are situated in an enclosure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 10/953,755 filed Sep. 29, 2004, which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates generally to the cooling of electroniccomponents, and particularly to the use of fans for cooling electroniccomponents.

The cooling of electronic components such as high power density devices,(HPDDs) including high power density integrated circuits (IC's) andcentral processing units (CPU's) for example, is a significantconsideration in the design of computer servers, military avionicequipment, medical imaging equipment, and other systems employing highpower density electronic devices. The term HPDD used herein refers toheat generating devices having a heat flux in excess of 10Watts-per-square-centimeter. In addition to having variations in heatflux, HPDDs have various peak permissible temperatures which also affectcooling requirements Electronic systems are being designed for greatercomputational speed and power and smaller footprints. These design goalsresult in a HPDD that generates a lot of heat in a small area/volume.Heat dissipation is important in order to avoid IC and CPU degradation.Power densities of some electronic systems are as high as about 200watts per square centimeter (W/sq-cm), and the trend appears to bemoving upward. In addition to heat dissipation requirements that resultfrom heat generation, enclosure size constraints present designchallenges. For example, conventional computer servers typically employcircuit boards that are housed in enclosures with a height restrictionof 1.75 inches, referred to as a 1U application, with multiple circuitboards being stacked adjacent one another in a rack chassis. With atypical electronic component having an ambient use temperature of nogreater than about 120 degree-Celsius (deg-C.) and a junctiontemperature restriction of about 90 deg-C., cooling systems are employedto transfer the heat of the HPDD to the surrounding ambient. Typicalcooling systems include fans, blowers, heat sinks, and refrigerationsystems, which tend to increase in size as the heat transfer demandsincrease.

Accordingly there is a need for an efficient thermal management systemfor electronic components including high power density devices.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a cooling system for cooling a plurality of electroniccomponents comprises a centralized source comprising at least one microcooler configured to deliver a flow of a cooling medium and a pluralityof baffles configured to redistribute the cooling medium over theelectronic components. The electronic components are situated in anenclosure.

In yet another aspect, a cooling system for cooling a plurality ofelectronic components comprising at least one CPU and a set of remainingelectronic components, comprises a centralized source configured todeliver a flow of a cooling medium to the CPU and generate an exitstream of the cooling medium. The cooling system further comprises aplurality of baffles configured to redistribute the exit stream to coolthe remaining set of electronic components, wherein the CPU andremaining set of electronic components are situated in an enclosure.

In another aspect, a method for cooling a plurality of electroniccomponents comprises delivering a cooling medium from at least one microcooler, and redistributing the cooling medium using a plurality ofbaffles over the plurality of electronic components.

In yet another aspect, a method for cooling a plurality of electroniccomponents comprising at least one CPU and a remaining set of electroniccomponents, comprises delivering a cooling medium from a centralizedsource and distributing the cooling medium over the CPU and generatingan exit stream. The method further comprises redistributing the exitstream using a plurality of baffles over the remaining set of electroniccomponents.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the exemplary drawings wherein like elements are numberedalike in the accompanying Figures:

FIG. 1 illustrates an exemplary cooling system for electroniccomponents;

FIG. 2 illustrates a second exemplary cooling system for electroniccomponents;

FIG. 3 illustrates a third exemplary cooling system for electroniccomponents;

FIG. 4 illustrates a fourth exemplary cooling system for electroniccomponents;

FIG. 5 illustrates a fifth exemplary cooling system for electroniccomponents;

FIG. 6 illustrates a sixth exemplary cooling system for electroniccomponents;

FIG. 7 illustrates a seventh exemplary cooling system for electroniccomponents; and

FIG. 8 illustrates an eighth exemplary cooling system for electroniccomponents.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed herein are cooling systems for cooling a plurality ofelectronic components. The cooling system comprises a centralized sourceconfigured to deliver a flow of a cooling medium and a plurality ofbaffles configured to redistribute the cooling medium over theelectronic components. The electronic components are situated in anenclosure. FIG. 1 illustrates an exemplary cooling system 2 for coolingelectronic components. The electronic components are enclosed in anenclosure 4. The cooling system 2 comprises a centralized source 12configured to deliver a flow of a cooling medium over the electroniccomponents situated within the enclosure 4.

In some embodiments, the electronic components comprise high powerdensity device such as a high-end integrated circuit (IC) for use in aserver computer system using at least one fan, such as a microcompressor, herein after called a micro cooler and a high flux heatexchanger, The fan is sized for applications having a dimensionalrestriction of 1.75 inches (“1U” applications). In some embodiments, thefan may be sized for 2U applications. In some embodiments, thecentralized source 12 comprises at least one micro cooler. Asillustrated in FIG. 1, the centralized source 12 comprises two fans suchas micro coolers 13 and 14. The micro coolers 13 and 14 are designed todeliver high flux of cooling medium such as air at sufficiently highenough pressure to over come the pressure looses in the system. The termhigh flux air used herein refers to airflow on the order of about atleast 25 CFM (cubic feet per minute).

In an exemplary embodiment described herein, the enclosure 4, in whichthe electronic components are situated, is a computer server box. Theenclosure 4 is configured to have a bottom surface 6, a top surface (notshown) and two side-walls 8 and 10. While the embodiments describedherein depict a computer server box as an exemplary high power densitydevice, it will be appreciated that the disclosed cooling systems mayalso be applicable to other high power density devices, such as militaryavionics and medical imaging components and equipment, for example. Theelectronic components described herein are heat-generating devices.These components are required to be cooled to a certain temperature forenhanced life and to improve their performance.

The electronic components typically include, for example, a plurality ofcentral processing units (CPUs) 20 and 22, disk drive 28, and a powersupply unit 36. The enclosure 4 may also comprise other componentsincluding but not limited to a graphic card (not shown). In operation,the cooling medium such as air from the micro coolers 13 and 14 is firstblown over the CPUs 20 and 22 and generates an exit stream 24. Thecooling system may further comprise converging channels 16 and 18wherein the CPUs 20 and 22 are placed in series (with respect tocentralized source 12) within a converging duct 17 formed by thevertically placed solid converging channels 16 and 18. In an alternativeembodiment (not shown), CPUs 20 and 22 are situated in parallel withrespect to centralized source 12.

The converging duct 17 ensures that the CPUs receive at least some flowof the cooling medium even when one of the micro coolers fail. The CPUsare the highest power density device in the server box, and an efficientcooling system is required to enhance the life of the CPUs 20 and 22.Accordingly, in the cooling system 2, as illustrated in FIG. 1, thecooling medium is first blown over the CPUs 20 and 22. The temperatureof the cooling medium is lowest at the inlet of the micro coolers 13 and14.

Embodiments with converging channels 16 and 18 provide an increase invelocity as the cooling medium passes over the first CPU 20. Theincreased velocity enhances the coefficient of heat transfer. Althoughthe temperature of the cooling medium increases as the cooling mediumflows through the converging channels 16 and 18, particularly due to theenhanced coefficient of heat transfer, cooling of the second CPU 22remains beneficial. In this design, the angles of the convergingchannels 16 and 18 with respect to the CPUs 20 and 22 are the same. Insome other embodiments, as illustrated in FIG. 2, wherein both the microcoolers are in operation, the angles may be modified to have a part ofthe cooler stream from one of the micro coolers flow directly to the CPU22, typically after being deflected off one of the converging plates.FIG. 2 illustrates a second exemplary cooling system 46, wherein theconverging channel 16 makes an wider angle compared to that made by theconverging channel 18 (with respect to the CPUs 20 and 22). Inoperation, the flow 19 from the micro cooler 13 flows to the CPU 20. Aportion of the flow 21 from the micro cooler 14 impinges on theconverging channel 16 and gets directed to the CPU 22. It should beunderstood by any person skilled in the art that the same configurationof the cooling system may be incorporated for one, two, or more than twoCPUs. In some embodiments, instead of placing the CPUs in series alignedin a straight line, CPUs may be placed in series about a straight line,but in a staggered arrangement.

The cooling system 2 of FIG. 1 further comprises a plurality of baffles30 and 32 to redistribute the exit stream 24 to a remaining set ofelectronic components (shown, for example, as the disk drive 28 and thepower supply unit 36). In one embodiment, the baffles 30 and 32 compriseone integrated structure. Baffles 30 and 32 are both vertically placedand run throughout the thickness 26 of the enclosure 4. In the specificembodiment of FIG. 1, the baffle 30 comprises a perforated plate or amesh, which plate or mesh is substantially hollow. Substantially hollowis defined herein as having an optimized open area to allow some flow ofcooling medium to move to the downstream area 34 in the enclosure 4 tocool some other electronic components (not shown). In some otherembodiments, wherein flow over downstream area 34 is not as important asflow in other areas of the enclosure, the baffle 30 may alternatively bea solid sheet. In the embodiment of FIG. 1, baffle 32 is a solid sheetmetal and is placed at an angle to the baffle 30. The baffle 30 acts asa deflector to move the cooling fluid to areas that need the coolingsuch as the power supply unit 36 and storage units such as the discdrive 28.

A portion 38 of the exit stream 24 is deflected by the perforated baffle30 and the remaining portion passes through the baffle 30 and flows tothe downstream area 34 to cool some other electronic components, ifpresent. A portion of the deflected cooling medium 38 is blown over thedisk drive 28 and once the cooling medium flows over the disk drive 28,the stream 42 flows to the power supply unit 36.

FIG. 3 illustrates a third exemplary cooling system 50 wherein enclosure4 comprises similar electronic components as shown in FIG. 1. In theexemplary cooling system as illustrated in FIG. 3, the baffle 30 is notattached to the sidewall 8 of the enclosure 4. The baffles 32 and 30 areplaced at a distance from the sidewall 8 of the enclosure 4 and create agap 52 for the cooling medium to flow. Baffle 32 is vertically placedthroughout the thickness 26 of the enclosure 4 and acts as a deflector.Baffle 30 may be a perforated plate or a mesh as mentioned in precedingsections. In this exemplary embodiment, the baffle 30 may alternativelybe a solid plate depending on the cooling requirement in the downstreamarea 34 of the enclosure 4. One solid plate example is an embodimentwherein the cooling requirement of the downstream area 34 is adequatelyhandled by the volume of the cooling medium passing through the gap 52.In operation, a portion of the exit stream 24 flows to the downstreamarea 34. The remaining portion of the exit stream 24 is deflected by thesolid baffle 32 and flows over the disk drive 28 and the power supplyunit 36 as shown in FIG. 2. The bypass stream 54 flowing through the gap52 may further be deflected through a number of small baffles 56, 58 and60, which ensure a more efficient distribution of the bypass stream 54over the downstream area 34.

FIG. 4 illustrates a fourth exemplary cooling system 70 for coolingelectronic components. The cooling system, as illustrated in FIG. 4,comprises three baffles, wherein the first baffle 72 is placed in ahorizontal position parallelly with the flow of the cooling medium. Thishorizontal baffle 72 may also be designated as a horizontal splitter,which is placed at half the height 26 of the enclosure 4. The baffle 72typically divides the exit stream 24 from the micro coolers 13 and 14into two streams, an upper stream 71 and a lower stream 78. Thehorizontal baffle 72 is fixed to a second baffle 70, which baffle 70 isplaced vertically. The vertical baffle 70 is fixed to the top surface(not shown) and the side-wall 8 of the enclosure 4 and to the verticalbaffle 70. The horizontal baffle 72 and the second baffle 70 areconnected to a third baffle 74 and a fourth baffle 76. The third baffle74 is placed vertically and is fixed to the bottom surface 4. The heightof the third baffle 74 is typically same as the height where thehorizontal baffle 72 is placed. In operation, the upper stream 71 isdeflected and flows over to the disk drive 28 and the power supply unit36. The lower stream 78 continues to flow to the downstream area 34 tocool the electronics components situated in that area.

Each of the baffles in the configuration as shown in FIG. 4 contributesto the efficient redistribution of the exit stream 24 from the CPUs 20and 22. The upper stream 71 impinges on the baffle 70, which blocks thetop half of the enclosure 4 above the horizontal baffle 72. Afterimpingement, the stream is deflected as shown by arrows 75. The fourthbaffle 76 is the deflector, which baffle 76 also deflects the flowmoving towards the power supply unit 36. The fourth baffle 76 may be avertical wall joining the horizontal baffle 72 and is fixed to thebottom surface 4 of the enclosure 4. This exemplary arrangement ofbaffles ensures that all of the lower stream 78 moves the downstreamarea 34 and prevents any back mixing of stream 78 towards the powersupply unit 36 or the disk drive 28.

In all the exemplary embodiments illustrated in FIGS. 1-4, the CPUs areplaced in series. Alternately, the CPUs may also be placed in parallelin the downstream area 34. In this configuration, the lower stream 78 isused to cool the CPUs placed in the downstream area 34. A converging andthen a diverging section (not shown) upstream of the CPUs, when the CPUsare placed in parallel ensures that the CPUs are uniformly cooled evenwhen one of the micro coolers fail. This converging (orconverging-diverging) section may have any relative position withrespect to the baffles but is necessarily placed upstream of the CPUs.

FIG. 5 illustrates a fifth exemplary cooling system 80 for coolingelectronic components. Similar to the configuration shown in FIG. 1, theelectronic components include a plurality of central processing units(CPU) 20 and 22, disk drive 28 and power supply unit 36. The coolingsystem 70 further comprises two baffles 83 and 81 in parallel to theCPUs and the disk drive 28, thereby creating a channel for the air-flow.In this exemplary embodiment, the micro coolers 13 and 14 are situatedwithin the enclosure 4. Due to the suction of air, the suction side ofthe micro coolers 13 and 14 is at a lower pressure than ambientpressure. The wall 11 adjacent to the disk drive 28 is configured tohave a plurality of opening for the ambient air 86 to flow inside theenclosure 4. As the pressure across the disk drive 28 is lower than thepressure at the suction of the micro coolers, the air is sucked inthrough the openings 29 in the wall 11 and gets deflected by the baffle85. Baffles 85, 83 and 81 create a flow path 88 for re-circulation ofair flow 86 back to the suction of the micro coolers 13 and 14. As shownin FIG. 5, the re-circulation flow 82 is recycled back to the suction ofthe micro coolers 13 and 14 through stream 82 and 84 respectively. Itshould be appreciated that the rectangular shape of the enclosure 4 asshown in the exemplary embodiment 80 may also be used for other bafflearrangements as shown in FIGS. 1-4 and 6-8.

FIG. 6 illustrates a sixth exemplary cooling system 89, wherein the CPUs20 and 22 are placed in parallel configuration with respect to thecentralized source 12. The air from the micro coolers 13 and 14 areblown over the CPUs 20 and 22 as shown in FIG. 6.

FIG. 7 illustrates a seventh exemplary cooling system 90 for coolingelectronic components. The electronic components include a plurality ofcentral processing units (CPUs) 20 and 22, disk drive 28 and powersupply unit 36. The enclosure 4 may also comprise other componentsincluding but not limited to a graphic card. The cooling systemcomprises a centralized source 12 comprising two micro coolers 13 and14. The cooling system further comprises a plurality of baffles 92, 94,96 and 98. The baffles may comprise separate units, or alternately thebaffles may comprise one integral structure. The CPUs 20 and 22 areplaced in series in the downstream area 34 of the enclosure 4. Thebaffles 92 and 94 are placed vertically, partitioning the flow from eachmicro cooler 13 and 14. The flow 106 from the micro cooler 14 is blownover the CPUs 20 and 22 directly as shown in FIG. 7. The flow 108 fromthe micro cooler 13 is deflected by baffles 96 and 98 to flow over thedisk drive 28 and the power supply unit 36. Baffle 96 may be a solidplate or perforated plate or mesh depending on the requirement of volumeof the cooling medium to cool the CPUs 20 and 22. The baffles 94 and 92may be movable about joints 100, 102 and 104 so that the positions of 94and 92 can be adjusted in case one of the micro coolers fails inoperation.

FIG. 8 illustrates an eighth exemplary cooling system, wherein thedesign of the baffles is configured to send more flow through the CPUs20 and 22. The baffles 112, 96 and 98 are positioned at the middle ofthe exit 116 of the micro cooler 13. This arrangement flows one half ofthe flow from the micro cooler 13 and the full flow from micro cooler 14to the CPUs 20 and 22. At joint 100, one additional baffle 114 is placedperpendicular to the flow from the micro coolers 13. The additionalbaffle 114 deflects the flow from the micro cooler 13 towards the CPUs20 and 22. The baffle 112 is movable at joints 100 and 116 and 118,which is at the center of the exit of the micro cooler 14. In theexemplary embodiment, the cooling system works efficiently in case of afailure in either of the micro coolers 13 and 14. In operation, in casethe micro cooler 13 fails, the baffle 112 may be moved to the position118, which allows a portion of the operating micro cooler 14 to blowcooling medium over the disk drive 28 and the power supply unit 36 usingthe baffles 96 and 98. In operation, in case the micro cooler 14 fails,the design of the baffles as shown in FIG. 8 allows a portion of theflow from the operating micro cooler 13 to flow over the CPUs 20 and 22using the additional baffle 114. In all embodiments described herein,the enclosure 4 is substantially free of stagnant recirculating pocketsof the cooling medium thereby enhancing the cooling efficiency.

The cooling systems described herein efficiently keep the temperature ofthe electronic components well within the limit, thereby enhancing thelife of the components in operation. The cooling systems describedherein keep the temperature of the CPUs below about 78 deg C., the diskdrive 28 below about 55 deg C. and the power supply unit below about 50deg C.

Disclosed herein are methods for cooling electronic components asdescribed in the preceding sections. A method for cooling a plurality ofelectronic components comprises delivering a cooling medium from acentralized source and redistributing the cooling medium using aplurality of baffles over the electronic components.

In yet another exemplary method for cooling a plurality of electroniccomponents comprising at least one CPU and a remaining set of electroniccomponents, the cooling medium is generated from a centralized source.The cooling medium is first distributed over the CPUs thereby generatingan exit stream. The exit stream is subsequently redistributed using aplurality of baffles over the remaining set of electronic components.

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims. Moreover, the use of the terms first, second, etc. do not denoteany order or importance, but rather the terms first, second, etc. areused to distinguish one element from another.

1. A cooling system for cooling a plurality of electronic components,said cooling system comprising: a centralized source comprising at leastone micro cooler configured to deliver a flow of a cooling medium; and aplurality of baffles configured to redistribute said cooling medium oversaid electronic components, wherein said plurality of baffles areconfigured to have different heights; wherein said electronic componentsare situated in an enclosure.
 2. A cooling system for cooling aplurality of electronic components, said cooling system comprising: acentralized source comprising at least one micro cooler configured todeliver a flow of a cooling medium; and a plurality of bafflesconfigured to redistribute said cooling medium over said electroniccomponents, wherein at least one of said baffles divides said flow ofsaid cooling medium horizontally into an upper stream and a lowerstream; wherein said electronic components are situated in an enclosure.3. The system of claim 2, wherein at least one of said baffles issituated in parallel to the flow of said cooling medium.
 4. A coolingsystem for cooling a plurality of electronic components comprising atleast one central processing unit (CPU) and a set of remainingelectronic components, said cooling system comprising: a centralizedsource configured to deliver a flow of a cooling medium to said at leastone CPU and generate an exit stream of said cooling medium; and aplurality of baffles configured to redistribute said exit stream to coolsaid remaining set of electronic components, wherein said plurality ofbaffles are configured to have different heights; wherein said at leastone CPU and remaining set of electronic components are situated in anenclosure.
 5. A cooling system for cooling a plurality of electroniccomponents comprising at least one central processing unit (CPU) and aset of remaining electronic components, said cooling system comprising:a centralized source configured to deliver a flow of a cooling medium tosaid at least one CPU and generate an exit stream of said coolingmedium; and a plurality of baffles configured to redistribute said exitstream to cool said remaining set of electronic components, wherein atleast one of said baffles divides said flow of said cooling mediumhorizontally into an upper stream and a lower stream; wherein said atleast one CPU and remaining set of electronic components are situated inan enclosure.
 6. The system of claim 5, wherein at least one of saidbaffles is situated in parallel to said flow of said cooling medium. 7.The system of claim 5, wherein said upper stream is deflected by avertical baffle, wherein said vertical baffle has a height less than theheight of said enclosure.
 8. The cooling system of claim 1, wherein atleast one of said baffles having different heights is configured toallow a portion of said flow of cooling medium to pass beyond said atleast one baffle and to deflect a remaining portion of said flow ofcooling medium.
 9. The cooling system of claim 1, wherein the pluralityof electronic components comprises at least two central processing units(CPUs) serially arranged with each other within said flow of coolingmedium to receive said flow of cooling medium originating from saidcentralized source and being delivered to said CPUs, such that said flowof cooling medium first impinges one of said at least two CPUs and thenanother of said at least two CPUs.
 10. The cooling system of claim 2,wherein said upper stream is deflected by a vertical baffle, whereinsaid vertical baffle has a height less than the height of saidenclosure.
 11. The cooling system of claim 2, wherein the plurality ofelectronic components comprises at least two central processing units(CPUs) serially arranged with each other within said flow of coolingmedium to receive said flow of cooling medium originating from saidcentralized source and being delivered to said CPUs, such that said flowof cooling medium first impinges one of said at least two CPUs and thenanother of said at least two CPUs.
 12. The cooling system of claim 2,wherein the plurality of baffles comprises a vertical baffle disposedproximate to a horizontal baffle, said horizontal baffle being orientedparallel to said flow of cooling medium, wherein the upper stream is onone side of said horizontal baffle and the lower stream is on the otherside of said horizontal baffle, wherein the upper stream is deflected bysaid vertical baffle and the lower stream flows downstream of saidvertical baffle.
 13. The cooling system of claim 2, wherein the verticalbaffle is edgewise connected to the horizontal baffle.
 14. The coolingsystem of claim 4, wherein at least one of said baffles having differentheights is configured to allow a portion of said flow of cooling mediumto pass beyond said at least one baffle and to deflect a remainingportion of said flow of cooling medium.
 15. The cooling system of claim4, wherein said at least one CPU comprises at least two CPUs seriallyarranged with each other within said flow of cooling medium to receivesaid flow of cooling medium originating from said centralized source andbeing delivered to said CPUs, such that said flow of cooling mediumfirst impinges one of said at least two CPUs and then another of said atleast two CPUs.
 16. The cooling system of claim 5, wherein said upperstream is deflected by a vertical baffle, wherein said vertical bafflehas a height less than the height of said enclosure.
 17. The coolingsystem of claim 5, wherein the at least one CPU comprises at least twoCPUs serially arranged with each other within said flow of coolingmedium to receive said flow of cooling medium originating from saidcentralized source and being delivered to said CPUs, such that said flowof cooling medium first impinges one of said at least two CPUs and thenanother of said at least two CPUs.
 18. The cooling system of claim 5,wherein the plurality of baffles comprises a vertical baffle disposedproximate to a horizontal baffle, said horizontal baffle being orientedparallel to said flow of cooling medium, wherein the upper stream is onone side of said horizontal baffle and the lower stream is on the otherside of said horizontal baffle, wherein the upper stream is deflected bysaid vertical baffle and the lower stream flows downstream of saidvertical baffle.
 19. The cooling system of claim 18, wherein thevertical baffle is edgewise connected to the horizontal baffle.